GlaxoSmithKline may be able to produce a vaccine in mass quantities to protect humans from bird flu by next year, the drugmaker said Wednesday following encouraging results from a clinical trial.
The prototype vaccine, which could potentially be used during a pandemic caused by the H5N1 virus, uses low doses of its active ingredient, meaning that greater quantities could be produced. The vaccine uses an inactivated strain of H5N1 that was isolated in Indonesia last year.
The results were based on a trial conducted on 400 adults in Belgium, using a vaccine including adjuvant, an ingredient added to vaccines to stimulate the immune system and increase the response to the vaccine.
"It's a good and exciting piece of science," Dr. David Nabarro, the United Nations' coordinator for avian and pandemic influenza, said. "But as with all new discoveries, quite a lot of work has now got to be done to establish its place in public health and pandemic preparedness."
Adding adjuvant to a vaccine allows makers to use less antigen, a key ingredient in vaccines. Previous attempts to create a pandemic vaccine have been disappointing, as they have required large amounts of antigen to provoke a strong immune response.
Using a proprietary adjuvant, GlaxoSmithKline PLC has apparently succeeded in producing an effective vaccine using a very low dose of antigen.
"This is very significant because it shows the principle that this adjuvant might do the job," said Dr. Albert Osterhaus, head of the virology department at Erasmus University in the Netherlands.
According to GlaxoSmithKline, the vaccine provoked a strong immune response in more than 80 percent of the people tested. "There is still a lot more work to be done with this program, but this validation of our approach provides us with the confidence to continue developing the vaccine," said J.P. Garnier, GlaxoSmithKline's chief executive officer.
While cautioning that the clinical results are still preliminary, some pandemic influenza experts are optimistic that this may ultimately result in the production of many more doses of pandemic vaccine. "It's still small numbers, but if GSK can corroborate this data, it shows that their adjuvant is good," said Osterhaus.
Because production capacity during a pandemic will be limited, using as little antigen as possible will be essential to mass-producing vaccine.
"With this adjuvant added to the vaccine, provided the rest of the tests are OK, you could make 10 times as much vaccine," said Osterhaus, emphasizing that it is still a two-dose vaccine.
Creating a prototype pandemic vaccine, however, does not guarantee that countries will be protected in the event of a flu pandemic. "This vaccine will only give protection against this particular H5N1 strain and possibly other H5N1 strains," said Osterhaus. Thus, if the next influenza pandemic is sparked by a subtype other than H5, much of this vaccine may prove of little use.
"It's a risk judgment for those potentially purchasing vaccine," said Dr. Angus Nicoll, influenza coordinator at the European Center for Disease Prevention and Control.
Because it is impossible to predict which influenza strain will spark the next pandemic, it is equally impossible to produce a vaccine that will be completely effective.
"It's a very difficult decision for a country to decide whether to invest in pandemic vaccines," said Nicoll. "If there is no H5N1 pandemic ... then eventually the vaccine expires and the resources invested in it are lost," he added.
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